From crystalline to amorphous: heterostructure design of MoO₂/MoS₂in situ supported by nitrogen-doped carbon with robust sodium storage at −40 °C

The restricted interfacial kinetics, increased charge-transfer resistance, and low diffusion coefficient are responsible for the unsatisfactory electrochemical performances of sodium-ion batteries at low temperatures. The commonly used anode materials are crystalline, which induces lattice strain and structure pulverization upon cycling. In this regard, replacing the crystalline material by its amorphous counterpart and further combining with a heterostructure design and carbon coating is believed to be an efficient approach to modify the sodium storage performance at low temperatures. Herein, cross-linked amorphous MoO₂/MoS₂in situ supported by nitrogen-doped carbon through a facile localized phase transformation strategy has been demonstrated, showing boosted sodium storage performances at both room and low temperatures. In particular, a high reversible capacity of 406.8 mA h g⁻¹ can be achieved up to 100 cycles (0.1 A g⁻¹) and 248.7 mA h g⁻¹ after 1500 cycles (1.0 A g⁻¹) at 25 °C. Even at −40 °C, a reversible capacity of 172.8 mA h g⁻¹ can still be maintained up to 100 cycles (0.1 A g⁻¹). Such superior electrochemical sodium storage properties should be mainly ascribed to the following factors: (1) convenient pathways from the cross-linked structure; (2) facile kinetics induced by the amorphous MoO₂/MoS₂ heterostructure; and (3) robust interface and low activation energy for charge transfer.